Error message when exiting product screen

Hi,
I have a woocommerce store and an issue has just arisen with the product pages in the back end. When I edit a product page and save it (or even just visit it and back out without amending it), as soon as I try to leave the page, a browser error pops up saying “Leave site? Changes that you made may not be saved”. Changes do appear to save but I still get the message.
All plugins and themes (Xstore) are updated to the latest version, cache has been cleared, permalinks re-saved, plugins disabled and so on.
This only happens on product pages and was wondering if this is something you guys had come across before?
Cheers ??